Oriented strand board, parallel strand lumber, flake board, and other wood-based compressed products are produced from wood particles, fibers, chips, and the like, which may be combined with a binder such as a resin or the like. Typically, the wood product and binder are first combined into a continuous low-density, mat-like product that is relatively pliable. The mat is fed into a press where it is compressed under high pressure to produce a relatively dense and rigid board. The mat may be heated during the compression process to promote binding and sometimes to facilitate curing of the resin.
In known continuous presses, such as the apparatus disclosed in U.S. Pat. Nos. 6,142,068 and 6,098,532, a pair of endless steel belts transports a mat between oppositely-disposed flexible intake plates and then over apparently fixed, heated press platens. The flexible plates and platens define a gap having a converging upstream portion wherein the mat is compressed to a finished thickness and a downstream portion wherein the mat is held at the desired size and heated to set the binder. Rollers are provided between the plates/platens and the belt to reduce friction. An array of hydraulic actuators is attached to the flexible plates for setting the shape of the belts and plates. Such systems require pulling the mat through a confined space during compression, which can be difficult and may limit the amount of compression that can be achieved. Moreover, significant heat is typically required to achieve the required heating through the material to fix the resinous binder, which can be difficult and expensive.
In U.S. patent application Ser. No. 10/368,950, Ser. No. 10/368,961, and Ser. No. 10/637,984, invented or co-invented by one of the inventors in the present application, a system and method for forming a compressed composite product using an oscillating compression pressing process is disclosed. All of these applications are herein incorporated by reference.
There remains a need for compression apparatus for efficiently compressing a mat having wood components and a binder.